Method for rinsing the backside of a semiconductor wafer

ABSTRACT

A method for rinsing the backside of a semiconductor wafer includes the operations of forming a wafer transport truck into a nozzle, and spraying a liquid from the nozzle onto the backside of the wafer. The nozzle may be disposed in a brush station, e.g., before an exit from a first brush box or before an exit from a second brush box.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 09/470,675,filed Dec. 23, 1999, and now U.S. Pat. No. 6,434,775, the disclosure ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to semiconductor fabricationand, more particularly, to a nozzle and a method for rinsing thebackside of a semiconductor wafer.

As the semiconductor industry moves to larger, e.g., 300 mm, wafers andto smaller, e.g., 0.18 μm and smaller, feature sizes, it is becomingincreasingly more important to rinse effectively and to control wafercontamination on the bottom side, i.e., the backside, of wafers duringwafer preparation operations. In one conventional brush station, theexit rinse manifolds, which are located at the exits from the first andsecond brush boxes of the brush station, include lower nozzlespositioned to spray deionized (DI) water onto the backside of a wafer.To provide the DI water sprayed from these lower nozzles with a path tothe center portion of the backside of a wafer, an aperture is providedin the wafer transport truck that carries the wafer through the exitrinse manifold. This aperture, however, does not permit an effectiveamount of the DI water sprayed from the lower nozzles to reach thecenter portion of the backside of a wafer. Thus, the lower nozzles inthe exit rinse manifold do not thoroughly rinse the backside of a wafer.

In view of the foregoing, there is a need for a method and device forrinsing a backside of a wafer that ensures that the backside of a waferis thoroughly rinsed.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention fills this need by providing anozzle that may be used to rinse the backside of a semiconductor wafer.The present invention also provides a method for rinsing the backside ofa semiconductor wafer.

In accordance with one aspect of the present invention, a nozzle isprovided. The nozzle includes a body having an entrance location and anexit location. The body has a curved exit surface defined at the exitlocation. An internal chamber is defined in the body below the curvedexit surface and a channel extends between the entrance location and theinternal chamber. A slit defines an opening in the curved exit surface.The slit extends from the curved exit surface into the internal chamber.The curved exit surface and the slit are configured to define a fannedspray when liquid flows out of the slit.

In one embodiment, the opening in the curved exit surface defines anelliptical path. In one embodiment, the slit is oriented at an angle ofabout 15 degrees to about 50 degrees relative to a horizontal plane. Ina preferred embodiment, the slit is oriented at an angle of about 30degrees to about 35 degrees relative to a horizontal plane. In oneembodiment, the fanned spray is directed toward a center portion of abackside of a semiconductor wafer.

In one embodiment, the body is a wafer transport truck. In oneembodiment, the fanned spray has a width greater than a width of thewafer transport truck. In one embodiment, the wafer transport truck isdisposed in a brush station. In one embodiment, the wafer transporttruck is disposed proximate to an exit from a first brush box. Inanother embodiment, the wafer transport truck is disposed proximate toan exit from a second brush box.

In accordance with another aspect of the present invention, a method forrinsing the backside of a semiconductor wafer is provided. In thismethod a wafer transport truck is first formed into a nozzle. A liquidis then sprayed from the nozzle onto a backside of a semiconductorwafer.

In one embodiment, the nozzle is configured to direct a fanned liquidspray toward a center portion of the backside of the semiconductorwafer. In one embodiment, the nozzle includes a curved surface in whicha slit is defined. In one embodiment, the nozzle is disposed in a brushstation. In one embodiment, the nozzle is disposed just before an exitfrom a first brush box. In another embodiment, the nozzle is disposedjust before an exit from a second brush box.

The nozzle of the present invention enables the backside of asemiconductor wafer to be thoroughly rinsed. This is beneficial becauseit not only helps minimize particle contamination on the backside of thewafer, but also neutralizes the pH of the surface of the backside of thewafer.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute partof this specification, illustrate exemplary embodiments of the inventionand together with the description serve to explain the principles of theinvention.

FIG. 1 is a simplified schematic diagram of wafer cleaning system thatshows two exemplary locations at which the nozzle of the presentinvention may be disposed to rinse the backside of a semiconductorwafer.

FIG. 2A shows a body that may be used to make a nozzle in accordancewith one embodiment of the invention.

FIG. 2B shows the body shown in FIG. 2A after section 122 has beenmachined to have a curved surface.

FIG. 2C is a cross-sectional view of section 122 taken along plane 2Cshown in FIG. 2B.

FIG. 2D shows the cut plane used to cut the body shown in FIG. 2B intotwo pieces.

FIG. 2E shows the body shown in FIG. 2B after the body has been cut intotwo pieces along the cut plane shown in FIG. 2D and additional machiningoperations have been performed.

FIG. 2F shows the body portions shown in FIG. 2E after they have beenjoined together to form a nozzle in accordance with one embodiment ofthe invention.

FIG. 2G illustrates the fanned pattern of liquid that flows out of theslit defined in the curved surface of the body in accordance with oneembodiment of the invention.

FIG. 3 is a perspective view of one piece of a two-piece nozzle formedin accordance with one embodiment of the invention.

FIG. 4 is a simplified side view of a two-piece nozzle formed inaccordance with one embodiment of the invention.

FIG. 5 is a simplified top view of the nozzle shown in FIG. 4 withaxles, pulleys, and O-rings mounted thereon for transporting asemiconductor wafer.

FIG. 6 shows a flowchart diagram illustrating the method operationsperformed in rinsing the backside of a semiconductor wafer in accordancewith one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Several exemplary embodiments of the invention will now be described indetail with reference to the accompanying drawings.

FIG. 1 is a simplified schematic diagram of wafer cleaning system 100that shows two exemplary locations at which the nozzle of the presentinvention may be disposed to rinse the backside of a semiconductorwafer. As shown therein, wafer cleaning system 100 includes brushstation 102 and spin, rinse, and dry (SRD) module 104. Those skilled inthe art are familiar with the details of brush station 102 and SRDmodule 104. Brush station 102 includes first brush box 102 a and secondbrush box 102 b. Inlet rinse manifold 106 a is disposed at the entranceto first brush box 102 a and exit rinse manifold 106 b is disposed atthe exit from first brush box 102 a. Exit rinse manifold 106 c isdisposed at the exit from second brush box 102 b. Each of rinsemanifolds 106 a, 106 b, and 106 c may include one or more nozzles forspraying a liquid, e.g., deionized (DI) water, onto the top side and thebottom side, i.e., the backside, of a semiconductor wafer.

Nozzle location 108 a is located just before the exit from first brushbox 102 a and nozzle location 108 b is located just before the exit fromsecond brush box 102 b. It should be noted that nozzle locations 108 aand 108 b refer to the location of the opening, e.g., slit, in thenozzle through which liquid is sprayed. In one embodiment, nozzlelocations 108 a and 108 b are located about 0.5 inch to about 2.5 inchesbefore the exit from first brush box 102 a and second brush box 102 b,respectively. In a preferred embodiment, nozzle locations 108 a and 108b are located about 1.5 inches before the exit from first brush box 102a and second brush box 102 b, respectively.

In operation, a wafer transport conveyor carries semiconductor wafer 110through brush station 102. As wafer 110 enters first brush box 102 a,wafer 110 is rinsed by inlet rinse manifold 106 a. After this rinsingoperation, brushes scrub wafer 110 in the presence of a desiredchemistry. Next, as wafer 110 is carried toward the exit from firstbrush box 102 a, the backside of wafer 110 is sprayed with liquid, e.g.,DI water, from a nozzle, the details of which will be described later,disposed at nozzle location 108 a. As wafer 110 exits from first brushbox 102 a, wafer 110 is further rinsed by exit rinse manifold 106 b.Once inside second brush box 102 b, brushes scrub wafer 110 in thepresence of a desired chemistry. After this scrubbing operation, thebackside of wafer 110 is sprayed with liquid, e.g., DI water, from anozzle, the details of which will be described later, disposed at nozzlelocation 108 b. As wafer 110 exits from second brush box 102 b, wafer110 is further rinsed by exit rinse manifold 106 c. After exiting fromsecond brush box 102 b, wafer 110 is transported to SRD module 104 inwhich well-known spin rinsing and drying operations are performed onwafer 110.

It will be apparent to those skilled in the art that, if desired, anozzle may be disposed at only one of nozzle locations 108 a and 108 b.For example, depending upon the particular chemistries being used toscrub the wafer, it may not be necessary to place a nozzle at both ofnozzle locations 108 a and 108 b. By way of example, if differentchemistries are being used in first brush box 102 a and second brush box102 b, then nozzles may be desirable at both nozzle locations 108 a and108 b. On the other hand, if different chemistries are not being used infirst brush box 102 a and second brush box 102 b, then it may bedesirable to have a nozzle only at nozzle location 108 b.

FIGS. 2A to 2G illustrate an exemplary method for making a nozzle inaccordance with one embodiment of the invention. FIG. 2A shows body 120,which serves as the starting point for the method. As shown therein,body 120 is a block having a generally rectangular shape. The firstoperation in the method of making the nozzle is to define a section thatwill serve as the exit location for body 120 and in which a curved exitsurface will be formed. As shown in FIG. 2A, section 122, which isindicated by dashed lines, has been defined as the section in which thecurved exit surface will be formed. FIG. 2B shows body 120 after section122 has been machined to have a curved surface. The contour of thiscurved surface is shown in FIG. 2C, which is a cross-sectional view ofsection 122 taken along plane 2C shown in FIG. 2B.

Once the curved exit surface has been formed in section 122, the nextoperation in the method of making the nozzle is to cut body 120 into twopieces. FIG. 2D shows the cut plane used to cut body 120 into twopieces. As shown therein, cut plane 124 passes through curved section122 and defines an angle, θ, relative to a horizontal plane. In oneembodiment, the angle, θ, is in a range from about 15 degrees to about50 degrees. In a preferred embodiment, the angle, θ, is in a range fromabout 30 degrees to about 35 degrees. If the angle, θ, is smaller thanabout 15 degrees, then the rinsing efficiency may decline due to aboundary layer on the wafer. If the angle, θ, is larger than about 50degrees, then the liquid spray from the nozzle may lift the wafer fromthe wafer transport conveyor.

After body 120 is cut into two pieces along cut plane 124, additionalmachining operations are performed on the two pieces. FIG. 2E shows bodyportion 120 a and body portion 120 b after these machining operationshave been performed. Considering first body portion 120 a, a small stepof material is machined from area 126 in curved section 122 a so that anarrow slit will be formed when body portions 120 a and 120 b are joinedtogether. The amount of material machined from area 126 may be varied toobtain a slit having a desired width. In one embodiment, the step ofmaterial machined from area 126 is in a range from about 2 thousandthsof an inch to about 4 thousandths of an inch. Turning to body portion120 b, a pocket of material is machined from area 122 b to defineinternal chamber 128 below the curved surface of section 122. In oneembodiment, internal chamber 128 has a generally elliptical shape, asshown in FIG. 3. Once internal chamber 128 is formed, body portion 120 bis machined to define channel 130, which will be used to deliver liquidto internal chamber 128.

FIG. 2F shows body portions 120 a and 120 b shown in FIG. 2E after theyhave been joined together to form the nozzle. Body portions 120 a and120 b may be joined together by any suitable joining technique. In oneembodiment, body portions 120 a and 120 b are joined together by amechanical fastener, as shown in FIG. 4. In operation, liquid from anappropriate liquid source, e.g., a DI water source, enters the inlet ofchannel 130, which serves as the entrance location for body 120. Theliquid flows through channel 130 and into internal chamber 128. Onceinternal chamber 128 becomes filled, liquid will begin flowing out ofslit 132 in a fanned pattern, as shown in FIG. 2G. The liquid flows outof slit 132 in a fanned pattern because internal chamber 128 equalizesthe liquid pressure along the slit and because both surfaces that definethe slit end at substantially the same point, i.e., there is nosubstantial overhang.

FIG. 3 is a perspective view of one piece of a two-piece nozzle formedin accordance with one embodiment of the invention. As shown in FIG. 3,body portion 120 b′ includes horizontal extension 120 b′-1 and verticalextension 120 b′-2 so as to form a portion of a wafer transport truck.Horizontal extension 120 b′-1 has cylindrical apertures 134 a and 134 bformed therein for receiving axles. As is well known to those skilled inthe art, these axles support the pulleys upon which the O-rings thattransport a semiconductor wafer are mounted. Horizontal extension 120b′-1 also has rectangular aperture 136 formed therein. As discussedabove, rectangular aperture 136 enables some, but not an effectiveamount, of the liquid sprayed from the bottom nozzles of a rinsemanifold to pass through horizontal extension 120 b′-1 and contact thebackside of a semiconductor wafer.

Vertical extension 120 b′-2 includes curved section 122 b′ in whichinternal chamber 128′ has been formed. In one embodiment, the depth ofinternal chamber 128′ is about 0.25 inch. As shown in FIG. 3, thesurface forming the back wall of internal chamber 128′ defines agenerally elliptical shape. In addition, surface 138, which defines oneside of the slit formed when body portion 120 b′ is joined together withbody portion 120 a′ (see FIG. 4), follows an elliptical path. Channel130′ extends from chamber 128′ to recess 140, which is configured toreceive a liquid supply tube.

FIG. 4 is a simplified side view of a two-piece nozzle formed inaccordance with one embodiment of the invention. As shown therein, bodyportions 120 a′ and 120 b′ are joined together by a pair of fasteners142 (only one of which is shown in FIG. 4) to form a wafer transporttruck. Body portion 120 b′ shown in FIG. 4 corresponds to body portion120 b′ shown in FIG. 3. Body portion 120 a′ has cylindrical aperture 134c formed therein for receiving an axle, as described above withreference to FIG. 3. Slit 132′ defines an opening in the curved exitsurface formed by curved sections 122 a′ and 122 b′ of body portions 120a′ and 120 b′, respectively. By way of example, the nozzle shown in FIG.4 may be integrated into a wafer transport conveyor system at one orboth of the nozzle locations shown in FIG. 1. In one embodiment, thenozzle is oriented so that the liquid spray from slit 132′ is directedtoward an oncoming semiconductor wafer. The fanned spray emanating fromslit 132′ contacts a center region of the backside of the wafer. Whenbody 120′ is a standard wafer transport truck, the fanned spray spreadsout beyond the width of the wafer transport truck and contacts a centerregion having a diameter of about 3.5 inches, even though the wafer istypically situated only about 0.125 inch above the wafer transporttruck.

Body 120′ and fasteners 142 may be formed from any suitable inert,nonmetallic material such as, for example, fluorinated polymers.Exemplary fluorinated polymers include polytetrafluoroethylene (PTFE),which is commercially available from E. I. duPont de Nemours and Companyunder the trademark TEFLON, and polyvinylidene fluoride, which iscommercially available from Elf Atochem North America, Inc. under thetrademark KYNAR. In addition to fluorinated polymers, body 120′ andfasteners 142 also may be formed from polymers such as polyethyleneterephthalate (PET) and polyetheretherketone (PEEK).

If desired, the two-piece nozzle shown in FIG. 4 may be formed as onepiece. By way of example, the nozzle may be formed as one piece using arapid prototyping technique, e.g., stereolithography. Alternatively, thenozzle may be formed as one piece using an appropriate moldingtechnique.

FIG. 5 is a simplified top view of the nozzle shown in FIG. 4 withaxles, pulleys, and O-rings mounted thereon for transporting asemiconductor wafer. As shown therein, body 120′ has slit 132′ andaperture 136 defined therein. Internal chamber 128′ is defined below thecurved surface in which slit 132′ is defined, as indicated by the dashedlines in FIG. 4. Axles 144 a, 144 b, and 144 c are disposed in apertures134 a, 134 b, and 134 c, respectively. Pulleys 146 a and 146 d aremounted on the opposing ends of axle 144 a. Pulleys 146 b and 146 e aremounted on the opposing ends of axle 144 b. Pulleys 146 c and 146 f aremounted on the opposing ends of axle 144 c. O-ring 148 a is disposed onpulleys 146 a, 146 b, and 146 c and O-ring 148 b is disposed on pulleys146 d, 146 e, and 146 f. In operation, a semiconductor wafer sits onO-rings 148 a and 148 b and is transported when O-rings 148 a and 148 bare rotated by a drive mechanism in one or more of pulleys 146 a-f.

FIG. 6 shows a flowchart diagram 200 illustrating the method operationsperformed in rinsing a backside of a semiconductor wafer in accordancewith one embodiment of the present invention. The method begins inoperation 202 in which a wafer transport truck is formed into a nozzle.By way of example, the wafer transport truck may be formed into anozzle, e.g., the nozzle shown in FIG. 4, using the method describedabove with reference to FIGS. 2A to 2G. Alternatively, the wafertransport truck may be formed into a one-piece version of the nozzleshown in FIG. 4 using a rapid prototyping technique, e.g.,stereolithography, or an appropriate molding technique. Next, inoperation 204, liquid, e.g., DI water, is sprayed from the nozzle onto abackside of a semiconductor wafer. In one embodiment, the nozzle isconfigured to direct a fanned spray toward a center portion of thebackside of the wafer. In one embodiment, the nozzle includes a curvedsurface in which a slit is defined. Once liquid is sprayed onto thebackside of the wafer, the method is done.

In one embodiment, the nozzle is disposed in a brush station just beforean exit from a first brush box. In this manner, the backside of thewafer can be thoroughly and effectively rinsed as the wafer istransported from the first brush box to a second brush box. In anotherembodiment, the nozzle is disposed in a brush station just before anexit from a second brush box. In this manner, the backside of the wafercan be thoroughly and effectively rinsed as the wafer is transportedfrom the second brush box to an SRD module.

As described herein, the nozzle of the present invention enables thebackside of a semiconductor wafer to be thoroughly rinsed. This isbeneficial because it not only minimizes particle contamination on thebackside of the wafer, but also neutralizes the pH of the surface of thebackside of the wafer.

In summary, the present invention provides a nozzle and a method forrinsing a backside of a semiconductor wafer. The invention has beendescribed herein in terms of several exemplary embodiments. Otherembodiments of the invention will be apparent to those skilled in theart from consideration of the specification and practice of theinvention. The embodiments and preferred features described above shouldbe considered exemplary, with the invention being defined by theappended claims.

What is claimed is:
 1. A method for rinsing a backside of asemiconductor wafer, comprising: forming a wafer transport truck into anozzle; and spraying a liquid from the nozzle onto a backside of asemiconductor wafer.
 2. The method of claim 1, wherein the nozzle isdisposed in a brush station.
 3. The method of claim 2, wherein thenozzle is disposed just before an exit from a first brush box.
 4. Themethod of claim 2, wherein the nozzle is disposed just before an exitfrom a second brush box.
 5. The method of claim 1, wherein the nozzle isconfigured to direct a fanned liquid spray toward a center portion ofthe backside of the semiconductor wafer.
 6. The method of claim 1,wherein the nozzle includes a curved surface in which a slit is defined.